feat: add ASR provider support for voice co-creation

backend/app/services/adapters/asr/demo.py

@@ -0,0 +1,57 @@
+"""Demo ASR adapter for local voice co-creation smoke tests."""
+
+from __future__ import annotations
+
+from fastapi import HTTPException
+
+from app.services.adapters.asr.models import TranscriptionOutput
+from app.services.adapters.base import BaseAdapter
+from app.services.adapters.registry import AdapterRegistry
+
+
+@AdapterRegistry.register("asr", "demo")
+class DemoASRAdapter(BaseAdapter[TranscriptionOutput]):
+    """Return transcript hints or text uploads without external ASR services."""
+
+    adapter_type = "asr"
+    adapter_name = "demo"
+
+    async def execute(
+        self,
+        audio_bytes: bytes,
+        file_name: str | None = None,
+        mime_type: str | None = None,
+        transcript_hint: str | None = None,
+        **kwargs,
+    ) -> TranscriptionOutput:
+        hint = (transcript_hint or "").strip()
+        if hint:
+            return TranscriptionOutput(
+                transcript_text=hint,
+                confidence=1.0,
+                provider=self.adapter_name,
+            )
+
+        if mime_type and mime_type.startswith("text/"):
+            text = audio_bytes.decode("utf-8", errors="ignore").strip()
+            if text:
+                return TranscriptionOutput(
+                    transcript_text=text,
+                    confidence=1.0,
+                    provider=self.adapter_name,
+                )
+
+        raise HTTPException(
+            status_code=503,
+            detail=(
+                "当前环境未配置真实语音转写，请先使用文本共创模式，"
+                "或在开发模式下提供 transcript_hint。"
+            ),
+        )
+
+    async def health_check(self) -> bool:
+        return True
+
+    @property
+    def estimated_cost(self) -> float:
+        return 0.0